Tafsir of Al-Mu'minoon 23:43

(No nation precedes its appointed term): That is, no nation among the destroyed nations precedes the time that has been set for their destruction. The word min (in min ummah) is added for emphasis to signify the generalization derived from the indefinite noun appearing in a negative context. The summary of the meaning is: No nation among the nations is destroyed before its term arrives.

(And they do not delay): That is, that term by an hour. The plural pronoun [in yasta'khirun] refers back to ummah (nation) based on its meaning.